While the seals of the present invention are not intended to be so limited, for purposes of an exemplary showing, they will be described in terms of their application to the relatively recently developed large hopper cars capable of carrying large loads and discharging their loads very quickly and efficiently. An exemplary car of the type contemplated is taught in U.S. Pat. No. 3,187,684 or U.S. Pat. No. 3,596,609. The bottom of such a car is made up of chutes which are partially intersected by the center sill of the car. Each chute comprises a pair of outer, substantially triangular hopper sheets depending downwardly and slightly inwardly of the car sides and a pair of substantially triangular inner hopper sheets located to either side of the car center sill. Each chute is provided with a pair of opposed hopper doors swingable between a closed position and a downwardly depending open position. Each hopper door is made up of two door panels joined together by appropriate transverse bracing and located to either side of the center sill. The panels of each door are appropriately hinged to transverse members of the car underframe. Opposed pairs of panels of an opposed pair of hopper doors cooperate with an inner and an outer hopper sheet located on the same side of the car center sill to close their respective chute.
The above mentioned U.S. Pat. No. 3,596,608 teaches various means whereby the bottom edges of the panels of an opposed pair of hopper doors form a seal therebetween to prevent leakage of a fine, granular commodity therebetween. Excellent results have been achieved, for example, when the opposed pair of hopper doors are so arranged that a first door of the pair closes slightly ahead of the second door of the pair. The bottom edges of the panels of the first door are configured to form a curved return flange which rests on the bottom edges of the panels of the second door when the hopper doors are in their closed position. As the hopper car is loaded, the hopper doors "seat" under the weight of the lading. The return flanges at the lower edges of the panels of the first door act as seals, bearing against and conforming to the contour of the bottom edges of the panels of the second door, thus providing a continuous metal-to-metal seal along these lines of contact between the panels of the opposed pair of hoppers doors. It has been found that no additional sealing is required at these interfaces between the panels of an opposed pair of hopper doors.
Hopper cars of the type contemplated are frequently used to haul fine, granular commodities such as wet rock, sand, aggregates, grain, or the like. It has been found that such fine, granular, fluid-type commodities can, under some circumstances, seep between the hopper door panels and the lower edges of the adjacent inner and outer hopper sheets. When the hopper doors are in their closed position, a metal-to-metal seal (like that formed between the lower edges of opposed hopper door panels) is not achieved between the hopper door panels and the adjacent inner and outer hopper sheets. This is particularly true when the opposed pairs of hopper doors "seat" under the weight of the lading.
The present invention is directed primarily to seals to prevent undesired seepage of a fine, granular commodity between the hopper door panels and the adjacent inner and outer hopper sheets, when the hopper doors are in closed position. To this end, elongated flexible sealing strips are removably and replaceably mounted along the inside surface of the inner and outer hopper sheets adjacent the lower edges thereof. Each sealing strip is of such width that it has a free longitudinal edge which extends below the lower edge of its respective hopper sheet. The amount by which this free edge extends below the lower edge of its respective hopper sheet must be such that when the hopper door is in its closed position, that panel thereof with which the sealing strip is to cooperate causes the free edge of the sealing strip to be bent inwardly. As a result, the longitudinal free edge of the sealing strip conforms to the nominally flat surface of the hopper door panel with which it cooperates, eliminating all gaps which might occur between the hopper door panel and the hopper sheet to which the sealing strip is attached.
As the hopper car is loaded, two things occur. The lower edges of the panels of the first hopper door of an opposed pair slide a fraction of an inch on the lower panel edges of the second hopper door of the pair, as the hopper doors "seat" under the weight of the lading and form the above described metal-to-metal seal between the abutting door panel lower edges. At the same time, the weight of the lading bears against the free edges of the flexible sealing strips. This forces the free edges tightly against the inside surfaces of their respective hopper door panels, thereby forming seals which will preclude the seepage of a fine, granular commodity between the hopper door panels and their adjacent inner and outer hopper sheets. When the hopper doors shift to their open position, they drop vertically away from the free edges of the seals, allowing the seals to bend downwardly as the lading discharges. The amount by which the free edge of each seal extends below the lower edge of its respective hopper sheet must not be so great that the seal is scrubbed by the lading at the instant of door opening.
A seal of the present invention may also be so located as to close a gap between the upper edge portions of the hopper door panels and the adjacent slope sheet, as will be described hereinafter.